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[Qemu-devel] Re: [RFC PATCH 0/5] Save state error handling (kill off no_


From: Anthony Liguori
Subject: [Qemu-devel] Re: [RFC PATCH 0/5] Save state error handling (kill off no_migrate)
Date: Tue, 05 Oct 2010 15:49:12 -0500
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On 10/05/2010 03:46 PM, Alex Williamson wrote:
On Tue, 2010-10-05 at 15:41 -0500, Anthony Liguori wrote:
On 10/05/2010 03:35 PM, Alex Williamson wrote:
I was thinking of making KVM VMs with assigned PCI devices
unsavable/unmigratable, but I wasn't thrilled with the
no_migrate solutions.  The more generic solutions seems to be
simply letting save handlers return an error if the device can't
be migrated.  This is also much more generic than a one-way
bit flip of the no_migrate flag.  For a vmsd based registration,
the pre_save() routine seems to be the right place to allow
devices to abort.  The series also carries the error back through
all the vmstate callers.  If this looks good, I'll give it some
more testing and submit as non-RFC.  Thanks,

Doesn't this mean that we don't fail the migration until after
transferring all of the memory contents?
That's the case with the current no_migrate implementation too, it
doesn't get called until qemu_savevm_state_complete().  Thanks,

Ouch, that's unfortunate but also should be easily fixable.

But making a save handler fail seems would make it impossible to get instant failure semantics.

Regards,

Anthony Liguori

Alex






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